1. Field of the Invention
The present invention relates to a suspended particle collecting member that becomes suitable when the suspended particle collecting member is installed in an image forming apparatus (such as a copying machine or a printer using electrophotographic recording technology), and to an image forming apparatus including the suspended particle collecting member.
2. Description of the Related Art
In general electrophotographic image forming apparatuses, a fixing unit heats a toner image formed on a recording material, and fixes the toner image to the recording material. Many types of toner materials contain wax components in addition to charging controlling agents, coloring agents, or binder resins (such as polyester resin or polystyrene resin). The wax components have various roles. The wax components serve as adjusting agents that adjust the melting temperature and the viscosity of toner. They also serve as adjusting agents that adjust the glossiness of a print image. They further serve as release agents for preventing offset development in which a portion of fused toner is moved to the surface of a fixing roller instead of to the recording material.
The wax components added to the toner are liquefied when the fixing unit is fixing the toner image, and large quantities of the wax components are, along with the fused toner, fixed after being transferred to the recording material. However, quantities of the wax components are vaporized. The vaporized wax components become liquid or solid fine particles depending on the ambient temperature during suspension thereof, and the fine particles are scattered. The fine particles are moved out of the fixing unit along rising air currents that are generated by the heat of the fixing unit and along air currents that are generated by the recording material that is conveyed.
When fixing temperature increases as the speed of the image forming apparatus increases, larger quantities of the wax components are vaporized. The wax components that are moved out of the fixing unit may adhere to various locations in the image forming apparatus. For example, when the wax components adhere to a conveying roller or a conveying guide for conveying the recording material, the wax components prevent the conveyance of the recording material and reduce the coefficient of friction of the conveying roller. Therefore, it is necessary to suppress leakage of the wax components to the vicinity of the fixing unit.
In a fixing unit disclosed in Japanese Patent Laid-Open No. 11-184293, the following technology is discussed. That is, an air blocking member that blocks the flow of air is provided in a gap (provided between a fixing rotating member and an inner wall of a housing), so that the flow of air in the housing is suppressed, and leakage of vaporized release agent is prevented from occurring. It is possible to filter suspended particles by disposing, for example, a nonwoven filter or an activated carbon filter in, for example, an exhaust duct disposed between the vicinity of the fixing unit and a location that is outside of the fixing unit. However, when an air blocking member is provided as mentioned above, although the vaporized release agent leaks out from the fixing unit less often, water vapor that is generated from the heated recording material tends to accumulate in the fixing unit, as a result of which dew condensation tends to occur in the fixing unit. Therefore, further measures need to be taken to prevent, for example, adhesion of water droplets to the recording material, a conveying member, etc. Even in the case where, for example, the aforementioned nonwoven filter is used, air in the vicinity of the fixing unit similarly generally tends to accumulate. Therefore, it is necessary to take measures against, for example, a temperature rise in the image forming apparatus in addition to dew condensation.